The pipe must be totally clean, round, deburred so there are no rough edges, and long enough. The deburring tool can also be used as the depth gauge for you to ensure it is inserted all the way. On 1/2" copper, I measure very close to 1" using their deburring tool, give or take a very small amount.

Properly installed, a Sharkbite can rotate (it might be stiff, but it will). A compression stop won't. A compression fitting will seal (assuming you can get the ring on) if the pipe isn't quite round, a sharkbite may not.

I haven't started this yet, but the reason I wanted to go Sharkbite over compression is due to lack of room. There doesn't appear to be enough space to manipulate two wrenches (wrench and counter-wrench).